This is an application to become a member of the NICHD Pediatric Pharmacology Research Unit Network to increase the study of medications in pediatric subjects, increase understanding of developmental changes in drug metabolism, and increase labeling of drugs for the pediatric population. As part of this application, we propose to study the pharmacokinetics of morphine and its metabolism into glucuronides during a 72 hr infusion. The efficacy of morphine will be determined with validated pain scales and bispectral analysis of infant EEG. Another study proposes a randomized, blinded comparison of the development of tolerance and abstinence during treatment of neonates with fentanyl and morphine for sedation and analgesia during mechanical ventilation. Predictors of tolerance will be determined based on pharmacologic measures of exposure. The effectiveness of clonidine for treatment of abstinence syndrome in neonates will be determined in an open-label treatment. A third study will determine the systemic exposure to local anesthetics contained in the S-Caine topical local anesthetic patch.